Standard original equipment with new automobiles includes so-called gas caps which are threaded onto the upper open end of gasoline filler tubes and removed therefrom by mere finger pressure rotation. However, it is useful to have such gas caps include a locking means of some sort to prevent gasoline from being stolen from the automobile or to prevent vandals from inserting substances into the gasoline tank to cause malfunction or destruction of the engine.
In addition, local state requirements, such as those of California, require that the filler tube be modified so as to accommodate vapor boot systems upper end, or a cap which is to remain on the filler tube during filling to insure that gasoline vapors will not be released into the adjacent environment when the tank is being filled. Also, it is now a customary requirement that a relief valve be provided to prevent buildup of undesirably high tank pressures which can cause explosion, for example. Many of the known past filler tube lock closures are not fully effective for use with a vapor boot system.
Still further, some known lock closures or locking gas caps once applied become a permanent fixture which cannot be easily removed.
Yet other forms of known locking gas caps are relatively difficult to mount to the filler tube which makes the device undesirable or impractical for sales to the aftermarket.